Product dispensers may be used to dispense a wide variety of products. In one example, cleaning chemicals, in the form of solutions, powders, solids or pastes are dispensed out of product containers to be used for cleaning a wide variety of objects, such as laundry or dishes. In many industrial or commercial applications, product dispensers are housed in locations away from employees, making monitoring the amount of chemical remaining in the product dispenser difficult. Previous systems have been designed to detect the amount of chemical remaining in a dispenser by means such as inductance sensing, float switches, flow meters, optical refraction systems and conductivity probes.